JPS6286514A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain magnetic characteristics including large magnetic permeability and max. magnetic flux density and small coefft. of loss in a high-frequency region by incorporating a specific ratio of SiO and/or CaO into Mn-Zn ferrite and providing a specific average grain size thereof. CONSTITUTION:The material of this magnetic head is the Mn-Zn ferrite which contains 53-54.4mol% Fe2O3 and 15-70mol% ZnO and into which <=0.02wt% SiO and/or <=0.1wt% CaO is incorporated. The average grain size thereof is adjusted to <=80mum. The magnet head has a core having >=5,000G magnetic flux density at 20 deg.C, DC and 150e and is used at 0.5-10MHz recording freqency. Such magnetic head has the large strength at the grain boundary of the front core and has the excellent magnetic characteristics including the large magnetic permeability and max. magnetic flux density in the high-frequency region of 0.5-10MHz and small coefft. of loss. The magnetic head is thereby made usable for writing, reading out, erasing, etc., in magnetic recording in a computer, etc.

Description

BACKGROUND OF THE INVENTION Technical Field The present invention relates to a magnetic head. More specifically, the present invention relates to improvements in manganese-zinc ferrite cores used in computer heads.

Prior art In recent years, in the field of magnetic recording technology, there has been a strong demand for higher recording densities. The current situation is that efforts are being focused on the development of materials with a large amount of energy.

Conventionally, manganese-zinc ferrite has been used as a material for the magnetic herad core.

This applies to low frequency range, for example 0.1 to several tens of KHz.
shows a large effective permeability, but in higher frequency ranges the effective permeability is small.

Moreover, the loss coefficient becomes large.

Under these circumstances, various additives 1, such as calcium oxide and silicon oxide (Trans, Jpn.

In5t, Net, 2 P171 (1961
)), niobium oxide, etc. have been proposed in a predetermined amount.

However, even these are unsatisfactory in terms of magnetic permeability and maximum magnetic flux density in the high frequency range for achieving the high density recording currently required for computer heads.

The present inventors have proposed to contain a predetermined amount of niobium oxide, vanadium oxide, and calcium oxide to solve this problem (Japanese Patent Application Laid-open No. 16863/1983).
According to this proposal, a magnetic material exhibiting a very large effective magnetic permeability in the high frequency range of 0.5 to IOM)lz can be obtained.

Incidentally, the ferrite core of a computer head such as the Winchester type must have extremely high grain boundary strength.

The core front surface of a computer head is finished by mirror polishing, and is floated above the medium through a small gap during recording and playback, but the grain boundary strength of the grains is low and the grains fall onto the medium. This is because doing so will cause serious trouble.

However, all conventional Mn-Zn-based ferrites have low strength at grain boundaries, and many defective products have been found where grains may fall off during inspection.

Therefore, there is a need for a magnetic head with high grain boundary strength, high magnetic permeability and maximum magnetic flux density in a high frequency region, and low loss coefficient.

■ Purpose of the Invention The purpose of the present invention is to increase the strength of grain boundaries, increase the magnetic permeability and maximum magnetic flux density in the high frequency region,
An object of the present invention is to provide a magnetic head with a small loss coefficient.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the first invention provides a manganese-zinc ferrite containing 53° to 54 mol% of Fe2O3 and 15 to 17 mol% of ZnO, and 0.02% by weight or less of silicon oxide and/or 0.1% of calcium oxide. % by weight or less, the average grain diameter is 801L11 or less, and the magnetic flux density is 50
Has a core of 00G or more, recording frequency 0.5~10MH
This is a magnetic head characterized in that it is used in z.

Further, the second invention provides a manganese-zinc ferrite containing 53 to 54.5 mol% of Fe2O3 and 15 to 17% of ZnO, and 0.02% by weight or less of silicon oxide and/or calcium oxide. A material containing 0.1% by weight or less and 0.0% or less of niobium oxide, with an average grain diameter of 80% or less, and 20% by weight or less.
C, DC, 150eTc7) This magnetic head is characterized in that it has a core with a magnetic flux density of 5000G or more and is used at a recording frequency of 0.5 to 10MHz.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The core of the magnetic head of the present invention contains 53 to 54 Fe2O3.
．． A small amount of silicon oxide and/or calcium oxide is contained in the manganese-zinc ferrite containing 5 mol% and ZnOt-15 to 17 mol%.

Further, niobium oxide is contained as necessary.

The additional elements contained, silicon oxide and calcium oxide, are components for improving magnetic properties, especially magnetic permeability, in the high frequency range (0.5 to 10 MH2), and the content of silicon oxide is 0.02% by weight or less. Particularly preferred is a range of 0.01 to 0.015% by weight.

On the other hand, calcium oxide also improves the magnetic permeability in a high frequency region, and its content is preferably 0.1% by weight or less, particularly in the range of 0.02 to 0.09% by weight.

Although only one of these two components may be contained, in the present invention, since they exhibit a synergistic effect particularly in terms of loss reduction, it is preferable to use both in combination.

Note that when the content of silicon oxide above exceeds 0.02% by weight, the strength of grain boundaries decreases. Furthermore, if the content of calcium oxide exceeds 0.1% by weight, the strength of grain boundaries will decrease.

Furthermore, in the present invention, 0.02% by weight of niobium oxide
Hereinafter, it is particularly preferable to contain it in a range of 0.005 to 0.02% by weight.

Addition of niobium oxide further improves magnetic permeability in the high frequency range.

However, when niobium oxide exceeds 0.02% by weight, the strength of grain boundaries decreases.゛The total content of calcium oxide, silicon oxide, and niobium oxide is 0.
2 below the amount%, preferably t L < t* o, o o
s~0.15% by weight.

When the total content exceeds 0.2% by weight, the strength of grain boundaries decreases.

The composition of the manganese-zinc ferrite used in the present invention is F
e20353-54, 5% le%.

The reason why Zn0 is set at 15 to 17 mol% is because the combination of the ferrite composition in this composition range and the contained additives as described above allows for high frequency range (0.5 to 10 MH
z), it becomes a low-loss ferrite with very high magnetic permeability.

In addition, it has excellent properties such as low coercive force and high maximum magnetic flux density, and is suitable as a magnetic rad core material for high-density recording.

Good magnetic properties cannot be obtained with compositions other than this.

The core of the magnetic head of the present invention made of such a material is molded by the steps described below, and the average grain diameter of the core for the magnetic head after molding is preferably 80 L or less, particularly 1G to 50IL. This is because when this value exceeds 801LII, the strength of the grain boundaries decreases.

Furthermore, the eddy current loss also increases, with 17
The average grain diameter of this type of grain is JI 5-C-2583.
-1981, and is calculated using the following formula.

D=l/NXL/nX1000 (ILm) Here, D
: Average grain size (final m) N: Microscope magnification L: Length of a straight line n: Number of particles that intersect the straight line The one-dimensional value calculated using the above formula is roughly calculated by π/2
The three-dimensional value calculated by multiplying is the average grain diameter in the present invention. It is.

Do=Dxπ/2 Furthermore, the density of the core is preferably 99.5% or more of the theoretical density, especially 99.8 to 100%. This improves the strength of the grain boundaries and increases the magnetic field in the high frequency region. Characteristics improve.

The core of the magnetic head of the present invention is manufactured as follows.

That is, a predetermined amount of the above composition is mixed in powder form. For mixing, wet mixing such as an attritor is usually used.

Next, it is dried, calcined, pulverized with a ball mill, etc., and then dried. Thereafter, after molding according to a conventional method such as so-called cold pressing, it was heated to 1100 to 1400
Primary firing is performed at ℃ until the density reaches 95 to 98% of the theoretical density.

Then 99.5% of the theoretical density at 1100-1400°C while applying a pressure of at least 800 Kg/cm2.
Secondary firing is performed until the temperature reaches the above level.

That is, in the secondary firing step, a dense coating layer is formed to close the communicating holes, and then in the secondary firing step, the material is compacted while being externally pressurized to form a sintered body with desired magnetic properties.

When manufacturing the magnetic head core of the present invention, instead of the silicon oxide and calcium oxide described above, substances that can be converted into these substances by firing, such as carbonates, heavy acid salts, hydroxides, etc., may be used. can.

Further, the non-oxidizing atmosphere for the second firing can be formed using, for example, an inert gas or an inert gas with a controlled oxygen concentration, or can be formed by reducing pressure.

Pressure in the secondary firing can be performed using, for example, a hot isostatic press device.

In order to arbitrarily control the average grain size of the core material in the present invention to some extent, the calcination temperature may be varied between 800 and 1000C and the secondary calcination temperature may be varied between 1250 and 1350C during the manufacturing process.

The maximum magnetic flux density of such a core is 20℃, DC, 150e (7) B15 is 5000G or more, especially 5
It is 200-5400G. Also, 20℃, 0.5
mA, 3, 5MH2 Te (7) Initial magnetic permeability 900 or more, especially 900 to 1200, also initial magnetic permeability 800 at 5MH
The initial magnetic permeability is above 600, especially 600-750.

When a recording frequency of 0.5 to 10 MHz is used, extremely good electromagnetic conversion characteristics are exhibited.

There is no particular restriction on the shape of the core of the magnetic head of the present invention, and it may be of various known shapes, such as the core shape used in Winchester types, etc. Then, a slider or the like is attached in accordance with a conventional method. Assembled as a magnetic head.

(2) Specific effects of the invention The magnetic head of the invention is used for writing, reading, erasing, etc. in magnetic recording for computers and the like.

And 1. The core of the magnetic head of the present invention.

Zinc-based ferrite containing Fe2035% to 54.5% by mole and Zn015 to 17% by mole, silicon oxide 0.0%.
0.02% by weight or less and/or 0.1% by weight or less of calcium oxide, and if necessary, 0.02% of niobium oxide.
Weight% or less A-&& m 44 jW -+II J
L 7 114 tm / , / , - diameter is B0
The total length is less than m.

Therefore, the obtained magnetic head has extremely excellent magnetic properties such as high grain boundary strength in the front core, high magnetic permeability and maximum magnetic flux density in the high frequency range of 0.5 to 10 MHz, and small loss coefficient. have characteristics.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

[Example 1] Fe203, ZnO and MnO shown in Table 1 below
To the composition, powders of silicon oxide, calcium oxide, and niobium oxide were further added in the proportions shown in Table 1, mixed well, and then calcined at 850° C. for 120 minutes.

Next, after pulverizing this calcined product, a small amount of polyvinyl alcohol is added as a binder to form a compacted powder body, which is made into a compacted powder with 2% oxygen by volume and 98% nitrogen by volume. Q Wanihachi to One To Octopus ``I tripped over it and heated it to 96% of the theoretical density.

Next, this was applied using a hot isostatic pressure device at a pressure of 1000 kg/c.
+w2, sintered at 1200° C. to theoretical density.

Note that samples having various average grain sizes as shown in Table 1 were prepared by changing the calcination temperature from 850 to 1000°C.

From the ferrite thus obtained, according to the usual method, the magnetic path length is 4 mm, the thickness Q is 1 mm, and the gap is 0.002 mm.
A core was fabricated.

Then, a head was obtained by attaching a slider and providing a winding.

The following properties were measured for these samples.

(1) Grain boundary strength (%) Etching was performed for 2 minutes with a 25% hydrofluoric acid aqueous solution, and after etching, observation was made using an optical microscope (400x magnification).
The falling off area ratio (%) of grains was calculated.

(2) Bls Magnetic flux density B 15 (G) was measured at 20°C, direct current, and 150e.

(3) Le 3, 5 JL5 p-720℃, 0
．． Initial permeability at 5mA is 3.5MHz, 5MHz
, measured at 7MHz.

The results are shown in Table 1.

From the results in Table 1, the effects of the present invention are clear.

That is, compared to the sample of the present invention, the comparative sample has a B 15 of less than 5000G or a grain boundary strength of less than 95%.

100 at 3.5-7MHz than the inventive sample.
It can be seen that this is too low for practical use.

Claims (1)

[Claims] (1) 53 to 54.5 mol% of Fe_2O_3, ZnO
A material containing 0.02% by weight or less of silicon oxide and/or 0.1% by weight or less of calcium oxide with respect to manganese-zinc ferrite containing 15 to 17 mol% of 20℃, DC, 150e
1. A magnetic head characterized in that it has a core with a magnetic flux density of 5000 G or more, and is used at a recording frequency of 0.5 to 10 MHz. (2) The magnetic head according to claim 1, wherein the density of the core is 99.5% or more of the theoretical density. (3) 53 to 54.5 mol% of Fe_2O_3, ZnO
A material containing 0.02% by weight or less of silicon oxide, 0.1% by weight or less of calcium oxide, and 0.02% by weight or less of niobium oxide in a manganese-zinc ferrite containing 15 to 17 mol% of , the average grain diameter is 80 μm or less, 20 ° C., DC, 150
1. A magnetic head characterized in that it has a core with a magnetic flux density of 5000 G or more at e, and is used at a recording frequency of 0.5 to 10 MHz.